A standard modular shelf system is formed by four identical standards normally made of sheet metal and each formed with a row of attachments, and a plurality of normally rectangular shelf panels. The standards are set vertically at corners of the panels where they are attached to the panels. The result is a shelf system that can be modified, expanded, and taken down and reassembled relatively easily.
While such a shelf system is carrying a considerable load, it has little lateral strength and therefore needs to be stiffened if it is to withstand any type of lateral load. Thus as described in U.S. Pat. No. 4,648,517 of Schafer stiffeners are used. The simplest stiffener is one or more diagonal struts secured between the standards. Alternately panels can be used which are connected to the standards and extend vertically. Such panels not only stiffen the system, but form a side or back wall for the shelves, making the systems somewhat easier to use than purely open shelving.